The Supreme Court's recent ruling on federal health care reform may have settled legal concerns, but the heads of Maryland's top insurer and two largest medical institutions said there are still unanswered questions and worries about the law.

"There are many unknowns, given the complexities of the act," said Chester "Chet" Burrell, president and CEO of CareFirst BlueCross BlueShield. "There could be surprises and unintended effects because of the complexity. All of the regulations are still not out yet and so it's hard to know how it will work out in the final analysis."

Burrell was joined Monday by Ronald R. Peterson, president of the Johns Hopkins Hospital and the Johns Hopkins Health System, and Robert A. Chrencik, president and CEO of the University of Maryland Medical System, in talking about reform during a session with members of the Greater Baltimore Committee. It was their first extensive public remarks since the nation's highest court upheld President Barack Obama's landmark legislation last month.

The three men all support reform and have participated in the state's aggressive efforts to begin implementing the law. Maryland was an early adopter despite the legal limbo and had moved ahead with aspects of the law, including creating exchanges where people eventually will buy coverage.

But the executives, who will be responsible for the law's implementation at their organizations, said they are concerned about costs and whether there will be enough doctors to treat millions of new patients. It remains unclear what the standard insurance plan will look like under reform and how the exchanges will work.

A third of the 750,000 uninsured Marylanders are expected to gain coverage in 2014, the first year the law is fully implemented.

Another major provision of the law calls for expanding Medicaid, which insures the poor and disabled, although the Supreme Court ruled that states can't be forced to add people to the rolls. The program, supported by state and federal dollars, is already financially strained, Peterson said. He also believes the program is almost certain to be targeted for cuts as the nation seeks to reduce its deficit.

"We are on the one hand pleased the federal government is going to provide a substantial opportunity for states, including this one, to expand the Medicaid program," Peterson said. "But nevertheless the underlying budget is already huge and then there will be that additional pressure. It is a concern."

The hope under reform is that better-managed patient care will prevent minor health problems from turning into costly conditions. That in turn would make health care less expensive. The law includes money for pilot programs to look at ways to cut costs and operate more efficiently. But Burrell said there is no clear-cut answer yet on what programs will work, resulting in more uncertainty.

"The reason they chose that path is because it's not so self-evident what to do to control health care costs," Burrell said of Congress.

The political climate also raises questions about reform, the executives said.

Republicans have said they will try to repeal reform and are hoping to win seats during November's election to improve their chances. In the meantime, the House of Representatives is expected to vote on repeal legislation this week — its 31st attempt. The effort is not expected to be taken up by the Senate.

Chrencik doesn't think repeal efforts would succeed, but he said he predicts portions of the bill will be eliminated through legislation. He worries that that could also hurt funding.

"If you don't want to change the law you can starve the accountable care act into not being implemented in certain areas just by turning the funding down," Chrencik said.

Burrell said implementation so far has resulted in a 1 percent increase in the cost of insuring a patient.

Despite their concerns, the executives said they expect reform to stabilize premium costs in the future.

"We do believe that, by and large, this has an affect over the intermediate to longer term to hold down premium costs," Peterson said.

Hospitals will continue to implement practices to operate more efficiently no matter what happens with reform, Chrencik said. He cited electronic medical records, which allow doctors to better pinpoint treatment since they have immediate access to a patient's medical history.

"When that patient hits the door they have to know something about them," Chrencik said. "Otherwise they're going to end up doing all the imaging, all the laboratory work and other stuff that is costly."

The executives said they are prepared to address obstacles to implementing reform as they come up.

"I think there is hope," Chrencik said, "but it's not going to be easy at all."